Refrigerating apparatus



July 1956 E. w. ZEARFOSS, JR 2,753,693

REFRIGERATING APPARATUS Filed May 23, 1955 3 Sheets-Sheet 1 FIG. I

INVENTOR.

ELMER W. ZEARFOSS Jr.

BY M

ATTORNEY y 0, 1956 E. w. ZEARFOSS, JR 2,753,693

REFRIGERATING APPARATUS Filed May 23, 1955 5 Sheets-Sheet 2 INVENTOR.

ELMER W. ZEARFOSS Jr.

ATTORNEY y 1956' E. w. ZEARFOSS, JR 2,753,693

REFRIGERATING APPARATUS Filed May 25, 1955 3 Sheets-Sheet 3 INVENTOR.

ELMER W. ZEARFOSS Jr.

ATTORNEY FIG. 3

United States Patent REFRIGERATING APPARATUS Elmer W. Zearfoss, In, Philadelphia, Pa.

Application May 23, 1955, Serial No. 510,208

14 Claims. (Cl. 62-4) My invention relates to a refrigerating apparatus and it relates more particularly to a dual refrigerating apparatus of the type which has two evaporator circuits which are supplied with refrigerant by asingle motorcompressor unit and which are adapted to maintain the temperature of two separate compartments at different predetermined values.

One object of the invention is to produce an improved refrigerating apparatus of the type set forth.

A further object is to produce an improved refrigerating apparatus wherein the operation of the motorcompressor unit is controlled. by the low temperature evaporator circuit or its environment, and wherein the flow of refrigerant to the higher temperature evaporator circuit is controlled directly or by the respective environment.-

A still further object is to obtain flow control of the refrigerant within these circuits concomitant with selective distribution.

A still further object is to produce an apparatus of the type set forth which is inexpensive to produce and to maintain.

These and other objects are attained by my invention as set forth in the following specification and as illustrated in the accompanying drawings in which:

Figure l is a diagrammatic view showing one embodiment of the invention.

Figure 2 is a similar view showing a second embodiment of the invention.

Figure 3 is a similar view showing a third embodiment of the invention.

The embodiment of Figure 1 includes a compressor 16 for compressing the spent refrigerant, a condenser 12 for liquefying the refrigerant and a capillary tube 14 for carrying the liquid refrigerant from the condenser to the evaporator circuits. In capillary tube 14' a pressure drop takes place and some of the liquid refrigerant changes state, so that a mixture of liquid and flash gas is delivered to a substantially non-restrictive. tube 16 at a point 18. Tube 16 leads to the bottom of a. blind accumulator 22 within which is a riser or stand pipe 24 provided with a bottom metering hole 26. The portion 28 of tube 16 above point 18 leads to a restrictor 30. through which refrigerant is further expanded. and delivered to the inlet end of a relatively low temperature evaporator 32, the outlet end of which leads to nonrestrictive tube 34. Tube 3'41 is. wound, one or more times, about the upper portion of the accumulator 22, as at A, and is brought into heat exchange with capillary tube 14, as at B. From heat exchange point B, tube 34 leads to the inlet of a relatively high. temperature evaporator 36. A tube 38 leads from the outlet of evaporator 36, and is wound about accumulator 22 as at C, and is brought into heat exchange with a, lower portion of capillary 14 as at D'. The heat exchange at- D is conventional and no further reference thereto is needed. Associated with evaporator 32" i'sa bulb 40 which, when the temperature of evaporator 32 falls'to the desired value, operates in the well known manner, to open a normally closed switch 42 to de-energize the compressor 10 and vice versa. Associated with evaporator 36 is a similar bulb 44 working through a higher temperature range which, When the temperature of evaporator 36 falls to the desired value, also operates in the well known manner to open a normally closed switch 46 to de-energize heater 48 and vice versa.

The operation is as follows:

At the beginning of a cycle, and with thetemperatures of evaporator 32 and 36 above the desired respective values, switch 42 will energize the compressor and switch 46 will energize heater 48. Under these conditions, the liquid refrigerant delivered by capillary tube 14 will fill the lower portion of tube 16 and a mixture of liquid and gaseous refrigerant will flow through tube 28-, and restrictor 30 to low-temperature evaporator 32. This takes place because of the low pressure in evaporator 32 and because the relatively high temperature of the accumulator 22 at the beginning of the cycle prevents the flow of refrigerant into the accumulator. As evaporator 32 is refrigerated, its frost point advances and by virtue of the pressure drop across restrictor 30, liquid refrigerant reaching heat exchange A cools the accumulator and tends to condense the gas therein. Since heater 48 is energized, its thermal output opposes heat exchanger A. In addition, the lack of liquid refrigerant in evaporator 36 causes the gas flowing through tube 38 to superheat. The heat thus made available at heat exchange C, combined with the heat supplied by heater 48, is sufficient to counteract the cooling effect produced by heat exchange A and will insure continued flow of liquid refrigerant to evaporator 32 and thence to evaporator 36. The frost point advances further, and liquid refrigerant flows through tube 38 to heat exchange C. Heat exchange C then reverses its direction of heat flow, and cools accumulator 22 suificiently to overcome the effect of heater 48. This will condense the gas within the accumulator and will stop or reduce the flow of liquid refrigerant through restrictor 30-to the evaporators.

Again the lack of liquid refrigerant at heat exchange C willenable heater 48 to overcome the cooling effect of heat exchange A, thereby causing refrigerant in the accumulator to be discharged to the evaporators. This process continues until heat exchange C once again receives liquid and counteracts heater 48 and so on.

Hence the flow of liquid refrigerant to evaporator 32 and evaporator 36 is controlled by the cyclic interaction of heat exchanger C with reference to heater 48, causing accumulator 22 to alternately store liquid and discharge liquid to the evaporators.

When the temperature of evaporator 36 falls to the desired value, bulb 44 operates to de-energi-ze heater 48. Upon de-energization of heater 48, the immediate flow of liquid refrigerant through tubes 34 and 38 will condense the gas. within the accumulator to draw the liquid refrigerant into the accumulator and thus stop: or reduce the flow of liquid refrigerant tothe evaporators. Subsequently, evaporator 36 and tube 38' will be starved of liquid. In evaporator 36: this-gas will superheat' and heat exchanger C will warm the accumulator. However, as long as tube. 34. contains liquid, heat exchange A. will overcome this effect and liquid refrigerant will continue to be drawn. into the accumulaton. But, as heat exchange A becomes starved of liquid, the rise in temperature there.- in cooperates effectively with heat exchange C to displace liquid refrigerant from the accumulator into evaporator 32', until a fall in temperature at heat, exchange A again condenses gas in the accumulator to repeat the processes described. The. mechanism of How control whereby evaporator 32 only" is refrigerated coincidesiwi'th the principle involved when both evaporators are refrig erated. Distinction resides in the fact that heat exchanger A and heat exchanger C respectively, are the dynamic elements in the two instances cited. When the temperature of evaporator 32 falls to the desired value, bulb 48 de-energizes compressor 10.

It is to be noted, that restrictor 30 influences the heat exchanger A and heat exchanger C. Increasing the value of restrictor 3!) causes a corresponding increase in the temperature differential at saturation across heat ex change A from tube 34 to accumulator 22, and increases the ability of heat exchange A to cool the ac-cnmulator and condense gas therein. Simultaneously, the temperature differential between superheated gas in tube 38 and the accumulator is decreased, thus proportionately decreasing the ability of heat exchange C to heat the accumulator, and evaporate the liquid therein. Hence restrictor 30 is readily designed to balance the heat exchange effect of exchanger A and exchanger C thereby achieving flow control of evaporator 32 when heater 4a is de-energized. When heater 43 is energized, the disturbance of the heat balance causes evaporator 36 to be refrigerated, and the consequent reversal of heat how in exchanger C easily restores the balance. Heater 43 in some instances, may be attached to the pipe 38 comprising a portion of heat exchange C rather than to the accumulator directly.

The physical sizing or proportioning of the heat exchangers also provides flexibility to the design problem of heat balance. Therefore, in some instances restrictor 3t) can be omitted. The hydrostatic pressure exerted by the column of liquid in tube 16 plus the pressure drop through the evaporator circuits will effect a sufficient temperature differential between the refrigerant in the accumulator and the liquid in the tubes 34 and 38, to allow heat exchangers A and C to efiect condensation of gaseous refrigerant in accumulator 22.

in order to temper, or moderate the flow control char acteristics of accumulator 22, hole 26 is made of a predetermined capacity so that the fiow of liquid refrigerant out of the accumulator is retarded. This prevents a too sudden discharge of liquid refrigerant to the evaporator circuit and accordingly reduces over-ride of the system. Riser 24, serves to purge any non-condensing gases that may be present in the system and which tend to collect at the top of the accumulator. This is accomplished every time that liquid is expelled from the accumulator via hole 26. Stand pipe 24 and hole 26 are elements that need not be included in a basic embodiment of the invention.

Heat exchange B primarily is intended to keep the inlet to evaporator 36 defrosted during the refrigeration of evaporator 32. The transfer of heat from the relatively Warm capillary 14 to the pipe 34 superheats the gas exchanger A and also erases liquid surges that may occasionally develop.

In the embodiment of Figure 2, tube 34', which leads from evaporator 32 is first brought into heat exchange with capillary tube 14, at E, and is then wound around accumulator 22' in the form of a heat exchange A before it enters evaporator 22 in the form of a heat exchange A before it enters evaporator 36'. In this embodiment liquid refrigerant will flow to evaporator 32', heat exchange A, and evaporator 36. Again, in order to achieve this, I provide heater 48, the output of which is enough to overcome the refrigeration effect of heat exchange A. This keeps accumulator 22 gas-bound and keeps liquid refrigerant flowing through the circuit, as stated, until the temperature of evaporator 36' falls to the desired value, whereupon bulb 44 will de-energize heater 48'. De-energization of the heater allows the liquid refrigerant flowing through heat exchanger A to condense the gas in the accumulator so as to draw liquid refrigerant into the accumulator thereby eifecting the starvation of evaporator 36 and tending to starve heat exchange A. Heat exchange A will then cause accumulator 22' to cyclically discharge and intake liquid refrigerant to control the flow of refrigerant to evaporator 32 in the manner set forth in connection with the embodiment of Figure 1. Heat exchange E cooperates in this process by reducing the amount of thermal inertia and over-ride in the flow control and in this particular in stance is comparable to the dampening efiect produced by heat exchange C in Figure 1. When the temperature of evaporator 32 falls to the desired value, bulb 40 will open switch 42 to de-energize the compressor it).

It will be noted that the second heat exchanger or accumulator 22 is omitted in the present embodiment, and that when both evaporator 32 and 36 are refrigerated control of refrigerant is provided by a conventional sump 50.

Since except as explained above, the structure and operation of this embodiment is the same as that of Figure 1, the prime of the reference numerals used on Figure 1 have been applied to the present embodiment.

The embodiment of Figure 3 includes compressor 10a, condenser 12a, capillary 14a, heat exchange D, restrictor 30a, evaporator 32a, evaporator 36a, bulb 4&1, switch 42a, bulb 44a, switch 46a and heater 48a, all of which are constructed and operate in the same manner as the corresponding parts of the embodiment of Figure 1. However in this embodiment, capillary 14a leads to nonrestrictive tube 52 which is connected to evaporator 32a by means of restrictor 30a.

Tube 52 is also connected by essentially non-restrictive tubes 54 and 56 to two separate accumulators 22a and 22b which are provided with risers 24a and 24b which correspond to riser 24 of the embodiment of Figure 1.

It will be noted further, that evaporator 32a is series connected to evaporator 36a by means of a pipe 58 which is heat exchanged with capillary 14a at F and is then Wound around accumulator 22b in the form of a heat exchange 60 before entering evaporator 36a. The refrigerant leaving evaporator 36a flows through pipe 62 which is wound around accumulator 22a in the form of a heat exchange 64.

At the beginning of a cycle when there is refrigeration demand in both evaporators, switch 42a will be closed to energize the compressor and switch 46a will be closed to energize the heater 48a. Because of heat transferred from superheated gas in coil 60 to accumulator 22b (plus the output of heater 48a) and from superheated gas in coil 64 to accumulator 22a, no liquid refrigerant will be drawn into either accumulator. Instead the refrigerant will flow into evaporator 32a and even when the frost point advances to coil 60, the output of heater 48a, by exceeding the cooling effect of coil 60, opposes entry of liquid refrigerant to accumulator 22b. The flow of liquid refrigerant advances and flows through evaporator 36a, and ultimately, to coil 64. Coil 64 then controls the flow of refrigerant to both evaporators by alternately drawing refrigerant from tube 52 into accumulator 22a and discharging refrigerant from accumulator 22a to evaporator 32a in the manner heretofore described. This operation continues until the temperature of evaporator 36a falls to the desired value and bulb 44a opens switch 46a to de-energize heater 48a.

In the absence of heat from heater 4811, the liquid refrigerant passing through coil 60 will condense the gases in accumulator 22b, which will now withdraw the liquid flowing through tube 52 to stop or reduce flow until evaporator 36b is starved. Under these conditions, accumulator 22b will respond to effects of coil 60 thereby controlling the flow of refrigerant to evaporator 32a. When superheated gas flows through coil 60 liquid refrigerant will be expelled from accumulator 22b and when liquid flows through coil 60 liquid refrigerant will be drawn into accumulator 22b. Bulb 40a, through switch 42b, will de-energize the compressor when the temperature of evaporator 32a falls to a predetermined value.

The embodiment of Figure 3.- ditfers from the embodiment of Figure l functionally, in that the present arrangement divides. the flow control feature and. applies the principles to individual accumulators. Hence a separate, accumulator is used with each heat exchange coil for achieving the two selective modes of operation possible with the system,

The heat exchange F is comparable to heat exchange E shown and described, for the embodiment of Figure 2.

I claim:

1. A refrigerating apparatus, including a compressor, a condenser connected to the discharge side of said compressor, a first evaporator, a passageway for delivering refrigerant from said condenser to the intake end of said first evaporator; an accumulator, a first conduit leading from said passage-way to said accumulator, a second evaporator, asecond conduit connecting the discharge side of said first evaporator to the intake side of said second evaporator, a third conduit connecting the discharge side of said second evaporator to the intake side of said compressor, refrigerating means normally operative to condense the refrigerant gas in said accumulator to draw liquid refrigerant from said passage-way into said accumulator and thus interrupt the flow of liquid refrigerant to said second evaporator, and heating means associated with said accumulator and operative to evaporate refrigerant in said accumulator to expel liquid refrigerant from the accumulator to said passage-way, the output of said heating means being greater than the cool ing effect of said refrigerating means to cause refrigerant to flow through said passage-way to said second evaporator as long as said heating means is energized.

2. The structure recited in claim 1 in which said refrigerating means includes a second conduit interposed said evaporators and brought into heat exchange relation with the accumulator to subject the latter to the cooling effect of the refrigerant flowing through said second conduit, and in which said heating means is in the nature of a controlled extraneous source of heat.

3. The structure recited in claim 2 and a first temperature responsive device associated with said second evaporator and operative to de-energize said heating means when the temperature of said second evaporator falls to a predetermined value, and a second temperature responsive means operative to de-energize said compressor when the temperature of said first evaporator falls to a predetermined value.

4. A refrigeration apparatus including a compressor, a condenser, a first evaporator, a passage-way for delivering refrigerant from said condenser to the intake end of said first evaporator, an accumulator, a first conduit connecting said passage-way with said accumulator, a second evaporator, a second conduit leading from the discharge end of said first evaporator to the intake end of said second evaporator, a portion of said second conduit between said evaporators being in heat exchange relation with said accumulator whereby the flow of liquid refrigerant through said portion of said second conduit operates to condense refrigerant gas in said accumulator to draw liquid refrigerant from said passage-way into said accumulator and thus substantially to reduce the flow of liquid refrigerant to said first evaporator, a heater associated with said accumulator the heat output of said heater being suflicient to overcome the cooling effect of the refrigerant flowing through said intermediate portion of said second coil and operative to evaporate refrigerant in said accumulator to expel liquid refrigerant from said accumulator to said passageway and said evaporators, a first temperature responsive device associated with said second evaporator and operative to energize said heater when the temperature of said second evaporator rises to a predetermined level and to de-energize said heater when the temperature of said second evaporator falls to a predetermined value, and a second temperature responsive device associated with said first evaporator and operative 6 to energize said compressor when the temperature of said first. evaporator rises to; a predetermined value and to deenergize said compressor when the temperature of said first evaporator falls to a predetermined value.

5. The structure recited in claim 4 and a third conduit leading from the discharge end of said second evaporator to said compressor, a portion of said third conduit between said second evaporator and said compressor being brought into heat exchange relation with said accumulator whereby the superheat of the refrigerant gas flowing through said last mentioned portion is added to-the output of said heater to overcome the cooling effect of the refrigerant flowing through said first mentioned portion, and whereby the cooling effect produced by the flow of liquid refrigerant through both of said portions is effective to condense refrigerant gas in said accumulator, the action of the heater notwithstanding.

6.. A refrigerating apparatus including a compressor, a condenser, a first evaporator, a passage-way for delivering refrigerant from said condenser to the intake end of said first evaporator, a first accumulator, a first conduit leading from said passage-way to said first accumulator, a second accumulator, a second conduit leading from said passageway to said second accumulator, a second evaporator, a third conduit leading from the discharge end of the first evaporator to the intake end of the second evaporator, an intermediate portion of said third conduit being brought into heat exchange relation with said first accumulator, whereby the flow of liquid refrigerant through said intermediate portion operates to condense refrigerant gas in said first accumulator to draw liquid refrigerant from said passageway into said first accumulator and whereby the flow of superheated refrigerant gas through said intermediate portion of said third conduit operates to evaporate refrigerant in said first accumulator to expel liquid refrigerant from said first accumulator to said passage-way and said first evaporator, a fourth conduit leading from the discharge end of the second evaporator to the compressor an intermediate portion of said fourth conduit being brought into heat exchange relation with said second accumulator whereby the flow of liquid refrigerant through said last mentioned intermediate portion of said fourth conduit operates to condense refrigerant gas in said second accumulator to draw liquid refrigerant from said passage into said second accumulator and whereby the flow of superheated gas in said last mentioned intermediate portion evaporates refrigerant in said second accumulator and expels liquid refrigerant from said second accumulator into said passage and to said first evaporator.

7. The structure recited in claim 6 and a heater associated with said first accumulator and operative to prevent condensation of refrigerant gas in said first accumulator, the cooling action of the refrigerant flowing through said first intermediate portion of said third coil notwithstanding.

8. The structure recited in claim 7 and a temperature responsive device associated with said second evaporator for deenergizing said heater when the temperature of said second evaporator falls to a predetermined value and vice versa.

9. The structure recited in claim 6 and a temperature responsive device associated with said first evaporator and operative to de-energize said compressor when the temperature of said evaporator falls to a predetermined value and vice versa.

10. In a refrigerating system including a compressor, a condenser, and a capillary tube for delivering liquid refrigerant to a first evaporator, a second evaporator in series flow relationship with said first evaporator, flow control means comprising; an accumulator, a passage-way communicating with said accumulator and the outlet of said capillary, first means adapted to cool said accumulator and to store liquid refrigerant therein and to oppose thereby the flow of liquid refrigerant to said second evaporator, and second means adapted to heat said accumulator and operable to discharge liquid refrigerant therefrom and to efiect thereby theflow of liquid to said second evaporator.

11. The structure recited in claim 10 and further characterized in that said first means comprises a conduit interposed said first and said second evaporators and in heat exchange with said accumulator, and in that said second means comprises an electrical resistance heater in heat exchange with said accumulator.

12. In a refrigerating system including a compressor, a condenser, a capillary, a first evaporator and a second evaporator connected in series flow relationship With said first evaporator, flow control means comprising: an accumulator, a passage communicating With said accumulator and the outlet of said capillary, a conduit interposed said first and said second evaporators and adapted to cool said accumulator and to store liquid therein so as to limit the flow of liquid refrigerant to said first evaporator and said conduit, and means operable under a modified condition of operation to heat said accumulator and to discharge liquid therefrom causing liquid to flow to said second evaporator, whereby said second evaporator may be selectively refrigerated.

13. The structure recited in claim 12 and further characterized in that said means is in the nature of an electrical resistance heater, and means for de-energizing said heater when the temperature of said second evaporator falls to a predetermined value.

14. The structure recited in claim 12 and further characterized by means operable by the rise, or by the fall of the temperature of said first evaporator to activate or deactivate said compressor.

References Cited in the file of this patent UNITED STATES PATENTS 

